For serious infections caused by Bacillus and Clostridia species the contagion is often the spore not the vegetative bacillus and represents an intervention point for controlling the infectious cycle. Germination is an essential early event for numerous infections including: anthrax (B. anthracis), C. difficile- associated infections (CDI), wound and GI infections, gas gangrene, tetanus, forms of botulism and other serious diseases. Germination can be rapid, occurring soon after spores enter the body, or can linger dormant for extended periods in the body before actual germination and onset of disease. Spores are hardy, not easily cleared from the body by natural means and are not susceptible to antibiotics. Their robust physical properties necessitate prolonged periods of antibiotic treatment with a high risk of developing serious drug intolerances and, in many instances (e.g., CDI and anthrax), residual spores cause re-infections after initial treatments are stopped. We hypothesize that blocking or delaying germination after exposure will be useful to slow the growth cycle and provide another line of defense in the instance of multi-drug resistance. It is also desirable to be able to induce germination, rendering the bacterium vulnerable to traditional antibiotics provided on a shorter treatment schedule. Research progress in anthrax spore germination are now to the level required to directly examine the germination processes and machineries, and develop means for real countermeasures. Using B. anthracis as the model system, this proposal uses validated, cross-species-conserved, genes required for bacterial spore germination to determine membrane topologies, protein interactions, complex formation and molecular mechanisms of the proteins responsible for this process. These studies will provide a solid basis for future translational work towards the goal of controlling germination as a means of medical countermeasures. PUBLIC HEALTH RELEVANCE: Spore-forming bacteria are of great concern in biodefense [e.g., anthrax] and emerging infections [e.g., CDI]. Detailed mechanistic understanding of spore germination will identify molecular targets for future small compound control, allowing either prevention or enhanced initiation of germination that result in bacterial forms far more susceptible to medical countermeasures.